Henry Maldonado, 55, woke up his girlfriend, Carmen Irizarry, 60, and her granddaughter, who goes by the name Heaven, in their 700 E. 156th St., near Jackson Avenue, about 5 a.m., sparking a fight, an NYPD spokesman said.
"A dispute ensued and it led to this," said NYPD Chief Jason Wilcox.
Maldonado, who is not biologically related to the girl, stabbed her five times in the left side of her chest, thigh, armpit and upper abdomen, police said.
Heaven escaped the apartment and raced upstairs to knock on the front door of her neighbor, Loretta Fleming, 47, the neighbor said. The bloodied girl is so short that her neighbor couldn't see her through the peephole.
"Who is it?" Fleming asked.
"It's me, Heaven. My grandfather went crazy. Please, help me! Help me! Oh God, he's going to come up here to get me!" the girl said, according to Fleming.
Fleming whisked her inside and reassured her, "He's not going to touch you. You're in my house. I'm going to call 911. You're going to be OK," she said.
Police and firefighters met the girl at the neighbor's apartment where they were directed down to the girl's eighth-floor home, officials said.
"They knocked on the door. They heard a male voice from inside, but no one answered," Wilcox said.
Smoke began seeping out of the apartment and the NYPD's Emergency Services Unit came broke down the door and found heavy smoke and fire inside, police said.
Firefighters put out the fire while police moved to subdue Maldonado, who refused to drop his blade until they shocked him with a Taser, police said.
BX ALL HANDS 700 E 156 ST, MULTIPLE DWELLING FIRE ON 8TH FLR, UNDER CONTROL— FDNYalerts (@FDNYAlerts) May 11, 2016
Irizarry, who suffered repeated stab wounds, was pronounced dead in her living room, police said.
Maldonado, who has 17 priors for charges including robbery and criminal possession of a weapon most recently in November 2015 when police found him carrying a gravity knife, officials said.
Maldonado has also been involved in a couple of domestic violence incidents with Irizarry, police said. The NYPD was last called to their home in 2005, police said.
He was still awaiting formal charges Wednesday, police said.
Maldonado survived a brush with death in August 2014 when a woman he was with pushed him out of the way of a driver who was trying to run them over near Bruckner Boulevard and 138th Street and fled the scene.
The woman, Christine Ayer, suffered several shattered ribs, two collapsed lungs, severe head trauma and was initially listed in critical condition, but later healed. The driver was later charged with attempted murder and is due back in court May 20, records show.
Maldonado was enraged by the incident, he told DNAinfo at the time.
"I felt angry, man. It was unnecessary," he said.
Ayer is a "sweet person," he said, and would "give you the last dime in her pocket," Maldonado added.
Photos posted on Facebook show Maldanado embracing both Irizarry and her granddaughter, Heaven.
Heaven was initially treated at Lincoln after the stabbing until she was transferred to Harlem Hospital where she is listed in stable condition, officials said.
Heaven had lived with Irizarry after her own mother lost custody of her, police said.
Irizarry, who worked at a shelter for elderly people with mental disabilities, did her best to take care of Heaven despite her often tumultuous relationship with her live-in boyfriend, neighbors said.
"She was great. As a motherly figure, she was No. 1. She was a great mother," said Rafael Rivera, 60, who lives down the hall and has known the couple for 30 years.
Irizarry and Maldonado often fought, Rivera said.
"I can't see through walls, but you could hear it. They had an up-and-down relationship," the neighbor added.
"Heaven, she's beautiful. Her name describes her. She's a heavenly child. She's innocent," Rivera said.
"She's an amazing little girl. She's still with us. Thank God."
Neighbors were amazed how Heaven managed to escape the horror in her home.
"She's strong to do all that after being stabbed. Big heart, little girl," Rivera said.